The present invention relates generally to satellite-based data communications systems and, more particularly, to power control systems for use with satellite modems and transmitter or transmitter/receiver (transceiver) units incorporated in such systems.
When operating a satellite-based data communications system, it is often important that all communication signals received by a given satellite have similar strengths. One reason for this is that, if one signal reaching a satellite is significantly stronger than the other signals reaching the satellite, then the significantly stronger signal may interfere with the other signals and, in doing so, may cause data carried by the other signals to be corrupted.
Although numerous phenomena (location in a beam, antenna pointing, etc.) may cause signal attenuation in satellite-based data communications systems, adverse weather is, perhaps, the most frequently encountered. The reason for this is that rain, clouds, and other adverse weather may cause signals transmitted by the transmitter or transceiver units of a satellite-based data communications system to be significantly attenuated and, thus, to have a reduced signal strength upon reaching a satellite.
To compensate for weather-induced signal attenuation, many satellite-based data communications systems employ various types of power control feedback to adjust the level of communication signals radiated by earth stations. For example, typical power control systems allow transmission signal strengths to be increased during periods of bad weather, thus compensating for any signal attenuation that may result from the weather. However, as is well known in the art, the input signal power that may be provided to a given transmitter or transceiver unit must be limited to prevent overdrive, which may cause the signals generated by the transmitter or transceiver unit to be significantly degraded. In short, if too much input signal power is provided to the power amplifier provided within a transmitter or transceiver unit, then the power amplifier may lose its ability to properly amplify signals and, in many instances, will generate significant amounts of in-band and out-of-band signal distortion. The in-band signal distortion may cause loss of communications connectivity on the link, and the out-of-band distortion may cause substantial interference with other signals being received by a satellite.
Accordingly, it is an object of the present invention to provide an improved power control system for use with satellite-based data communications systems.